Chair

ABSTRACT

A chair is equipped with a leg column  1 , a seat  3 , and a back support  4 . An intermediate supporting member  9  is fitted to an upper end of the leg column  1 , the seat  3  and a back frame  5  are fitted to the intermediate supporting member  9 , and the back support  4  is fitted to an upper end of the back frame  5  via a joint unit  11 . The seat  3  has an elongated shape when viewed from the top, and is fitted to the intermediate supporting member  9  to swivel horizontally. The back support  4  can be turned freely around a first axis  13  and also can be turned freely around a second axis  12 . Since the seat  3  and the back support  4  can be changed into various modes, a using mode of the chair can be changed variously.

TECHNICAL FIELD

The invention of this application relates to a chair.

BACKGROUND ART

As one type of the chairs, there is the swivel chair whose seat ishorizontally revolved. There are some swivel chairs that have thebackrest and others that do not have the backrest. In the swivel chairwith the backrest, normally a planar shape of the seat is formed as analmost square and, for example, the office chair is suitable for longsitting hours. Also, because of the presence of the backrest, therelative planar posture of the user to the chair can always be keptconstant when the user sits on the chair. Many of the swivel chairs withthe backrest are also equipped with the armrest.

In the prior art, improvement in the sitting feeling is a major problemin the swivel chair without the backrest as well as the swivel chairwith the backrest. The chair manufacturers pay special attention to thedevelopment of the chair structure that does not make the user tiredwhile such user sits on this chair for a long time. It is of courseimportant that the chair is comfortable to sit on. Accordingly, it isquite appropriate that the development resources are assigned to theimprovement in the sitting feeling, and the meaning is not lost evennow.

Meanwhile, in Patent Literature 1 (JP-A-10-215978), it is set forth thatthe resting tool on which the seated person can rest both arms andagainst which the seated person can lean forwardly is arranged to swinghorizontally. According to this configuration of this Literature, whenthe seated person is tired from the deskwork such as the operation ofthe personal computer, or the like, such seated person can take a restwhile leaning against the resting tool that has been turned to the frontside of the seated person.

DISCLOSURE OF THE INVENTION Problems that the Invention is to Solve

By the way, a large transformation in people's working style occurredrecently. More particularly, the spread of the free address system(non-territorial system) where an individual has no private desk andchair in the office, the circulation of the project system where a grouppursues a project at meetings, the development of thepersonalization/smaller scale exemplified in SOHO (small office, homeoffice), the progress of the network system business category whereindividuals in the same profession meet frequently to promote a businesswhile working together, the extension of the in-company businessestablishment where staffs of a company conduct independent businessesin the company, and the like occurred.

There is a trend toward the respect for individual liberty in thebackground to such transformation in people's working style. A humanpower of creation can be heightened by an interaction of the respect forindividual freedom with the deepening of communication, and it is as aresult understood that both the worker's satisfaction and theproductivity can be enhanced. Then, in order to either increase thedegree of personal freedom or deepen the communication, the free relaxedatmosphere is needed.

The chair is the furniture that touches the worker's body. But it ispossible to say that, in the prior art, the chair used in the non-familycase such as the office, or the like has seldom been developed from theviewpoint that such chair contributes to a creation of an atmosphere offreedom. Also, it is possible to say that, the novelty or variety ofmotion and the novelty of design, which allows the user to use the chairin a playful spirit, may be mentioned as conditions necessary for thechair that can contribute to a creation of an atmosphere of freedom.

On the contrary, when the person holds the meeting, the conference, orthe like in the office, or the like, it is common that such person usesthe materials, and the like. Therefore, it becomes a problem where thesematerials, etc. should be placed. The person can relax and take a reston the chair set forth in above Literature. But such a problem arisesthat, when the person intends to hold the meeting, or the like by usingthis chair, such chair lacks in versatility because a desk on whicharticles such as the materials should be put is needed separately.

The invention of this application has been made to improve such existingcircumstances.

Means for Solving the Problems

A chair of the invention of this application, includes a seat on which aperson sits; an almost plate-like back support having a supportingsurface against which a seated person is able to lean a back; and a backframe to which the back support is fitted via a portion that isdifferent from the supporting surface.

Then, the back support is fitted to the back frame in a condition thatat least one motion out of a first motion by which the back support isturned around an axis that extends in a direction to pass through thesupporting surface and a second motion by which the back support isturned from a fallen position in which the supporting surface isdirected forward to a horizontal position in which the supportingsurface is directed just upward is allowed.

In the invention of this application, both the first motion and thesecond motion provided to the back support are a novel motion that theconventional chairs do not possess respectively, and various uses thatthe chairs do not possess up to now can be offered to the user by thesenovel motions. For example, when the back support takes the secondmotion, the back support can be used as the backrest in its fallenposition and can be used as the armrest or the small table in itshorizontal position. The person who is sitting on the chair with aposture opposing to the back support can “play” by turning the backsupport while using the first motion. Also, because the back support canbe used variously or the novel motions of the back support are funny,this chair can contribute to creation of a relaxed environment.

The invention of this application contains many expanded modes(preferred modes). As one of these modes, the back support is formedinto a long and narrow shape that has a lengthwise direction and awidthwise direction when viewed from a direction facing to thesupporting surface, and the first motion is given to the back support byfitting the back support to the back frame such that the back support isturned around a fist axis that passes through an almost center portionin the lengthwise direction and the widthwise direction.

Because the back support is formed into an elongated shape, the shape ofthe back support can be changed to a lengthwise posture and a widthwiseposture, for example, according to the first motion. Therefore, when theback support is used as the backrest, the user can select the posture tomeet the user's liking or physique. Also, in a situation that the personwho is sitting on the chair to face to the back support contacts thebelly to the back support or rests the elbow on the back support, theuser can rest the belly or the elbow in a natural posture when the backsupport is set to assume the widthwise posture, and thus convenience inuse can be improved.

When the back support can make both the first motion and the secondmotion, preferably the using modes of the chair can be increased. Theinvention of this application contains the structures that permit theback support to take the first motion and the second motion.

More particularly, in this example, a rotary bearing is fitted to anupper end portion of the back frame such that the back support is turnedfreely from an almost forward posture to an upward posture when viewedfrom a side, and the back support is fitted to the rotary bearing toturn around axes that extend in a direction to pass through thesupporting surface of the back support and extend in a direction tointersect orthogonally with a rotating axis of a joint. Since the jointis rotated vertically only in this structure, the supporting structureof the back support becomes stout.

The reform measure for the sitting mode is also contained in theinvention of this application. In this reform measure, the seat isformed into a long and narrow shape that has the lengthwise directionand the widthwise direction when viewed from a top, and the seat issupported by legs to swivel horizontally around an almost center portionin the lengthwise direction and the widthwise direction.

In case the seat has a long and narrow shape when viewed from the top, arelative posture of the seat to the back support is changed when theseat is swiveled horizontally. In other words, not only the posture ofthe back support can be changed but also the posture of the seat can bechanged. As a result, variations of the using mode of the chair aretremendously increased, and thus convenience in use can be much moreimproved.

While the person is sitting astraddle on the seat, this seated personcan put articles on the back support or can rest the elbows on the backsupport after he or she positions the back support in front of him orher. In this case, because the seat has the long and narrow shape, theperson can sit astraddle on the seat in a relaxed posture. In otherwords, the user can select naturally either a mode in which the personsits on the chair with his or her knees close or a mode in which theperson sits astraddle on the seat with his or her knees apart. As aresult, such selection makes it more certain that the back support has awide variety of using modes.

In one preferable expanded example of the invention of this application,the back frame is supported by a leg column to swivel horizontally, anda swiveling center of the back frame coincides with a center of the legcolumn, and the seat is supported by the leg to swivel horizontallyaround a position that is deviated from a swiveling center of the backframe in a horizontal direction.

According to this structure, because the back frame can be swiveledhorizontally, the seated person can move the back support to anyposition beside him or her without change of the posture. Also, if acenter of the horizontal swiveling motion of the seat agrees with acenter of the leg column, it is possible that, because a center ofgravity of the seated person is too far from the leg column, the postureof the seated person will become unstable. In this event, a swivelingcenter of the seat is positioned eccentrically from the leg column, acenter of gravity of the seated person can be put as close as possibleto the leg column. As a result, stability of the chair can be improved.

In another expanded example of the invention of this application, thechair further includes an intermediate supporting member provided to anupper end of the leg column to swivel horizontally; where the back frameis fixed to the intermediate supporting member and also the seat isfitted to a portion, which is deviated from the leg column to an outsidewhen viewed from the top, of the intermediate supporting member toswivel horizontally. Since the back frame and the seat are fitted to thecommon intermediate supporting member, an overall structure of the chaircan be simplified.

In still another expanded example of the invention of this application,a planar shape of the seat and an outer shape of the supporting surfaceof the back support are formed into a bottle gourd shape, a middleportion of which in the lengthwise direction is formed to constitute anarrow portion having a narrowest width and an incomplete circularportion is connected to both sides of the narrow portion, respectively.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1(A) is a front view of a chair according to a first embodiment,and

FIG. 1(B) is a right side view of the chair according to the firstembodiment.

FIG. 2 is a plan view of the chair according to the first embodiment.

FIG. 3 is a sectional view viewed from a III-III line in FIG. 2.

FIG. 4 is an exploded perspective view of a seat receiver portion.

FIG. 5 is an exploded plan view of the seat receiver portion.

FIG. 6 is a partially broken plan view of the seat receiver portion.

FIG. 7 is a partially broken separated side view of the seat receiverportion.

FIG. 8(A) is a sectional view viewed from a VIIIA-VIIIA line in FIG. 6,FIG. 8(B) is a sectional view viewed from a B-B line in FIG. 8(A), FIG.8(C) is a sectional view showing a motion of a lever, FIG. 8(D) is asectional view showing another example of a lever holding means, andFIG. 8(E) is a plan view of the lever holding means in FIG. 8(D).

FIG. 9 is an exploded perspective view of a joint unit.

FIG. 10 is an exploded plan view of the joint unit.

FIG. 11(A) is a plan view of a joint unit, FIG. 11(B) is a side view ofthe joint unit, and FIG. 11(C) is a partially broken plan view of thejoint unit.

FIG. 12(A) is a longitudinal sectional side view of the joint unit, FIG.12(B) is a sectional view viewed from a B-B line in FIG. 12(A), and FIG.12(C) is a sectional view viewed from a C-C line in FIG. 12(A).

FIG. 13(A) is a longitudinal sectional side view of the joint unitshowing a state where a back support cannot be moved to a horizontalposition, and FIG. 13(B) is a plan view of the chair.

FIG. 14(A) is a longitudinal sectional side view when the back supportis in its horizontal position, FIG. 14(B) is a sectional view viewedfrom a B-B line in FIG. 14(A), and FIG. 14(C) is a plan view of thechair.

FIG. 15 is a plan view showing using examples of the chair.

FIG. 16 is a longitudinal sectional side view of a joint unit accordingto a second embodiment.

FIG. 17(A) is a longitudinal sectional side view of a joint unitaccording to a third embodiment, and FIG. 17(B) is a sectional viewviewed from a B-B line in FIG. 17(A).

FIG. 18 is a longitudinal sectional side view of a joint unit accordingto a fourth embodiment.

FIG. 19(A) is perspective view of a joint unit according to a fifthembodiment, and FIG. 19(B) is a longitudinal sectional side view of thejoint unit according to the fifth embodiment.

DESCRIPTION OF REFERENCE NUMERALS AND SIGNS

-   1 leg column (gas cylinder)-   2 leg-   3 seat-   4 back support-   4 a narrow portion-   4 b incomplete circular portion-   5 back frame-   8 seat receiver portion-   9 intermediate supporting body-   11 joint unit-   12 second axis-   13 first axis-   37 fixed bearing-   38 auxiliary bearing-   40 rotary bearing

BEST MODE FOR CARRYING OUT THE INVENTION (1) Outline of First Embodiment

FIG. 1 to FIG. 15 show a first embodiment. First, an outline of a chairwill be explained with reference to FIG. 1 and FIG. 2 hereunder. Thechair includes a leg 2 having a leg column 1, a seat 3 supported by theleg column 1 such that its height can be adjusted, a back support 4against which the seated person can lean, and a back frame 5 to whichthe back support 4 is fitted.

The leg 2 has a plurality of branch legs 6 that extend in a radialfashion from the leg column 1 when viewed from the top. A caster 7 isprovided to a top end of each branch leg 6. A gas cylinder whose innerand outer cylinders can be fitted mutually to move vertically and rotaterelatively is used as the leg column 1. In this example, an elevatingcylinder 1 a constitutes the inner cylinder, and an outer cylinder 1 bconstitutes the fixed cylinder.

A seat receiver portion 8 is provided between the leg column 1 and theseat 3. The seat receiver portion 8 has an intermediate supporting body(seat receiver base) 9 that is opened upwardly. A planar shape of theintermediate supporting body 9 is formed into a teardrop shape whosewidth dimension is increased gradually from one end portion to the otherend while rounding as a whole. Also, the intermediate supporting body 9constitutes a cubic boat shape both end portions of which are inclinedwhen viewed from the side while curving when viewed from the front.Also, the intermediate supporting body 9 is fixed to an upper end of theelevating cylinder 1 a at a portion located near the narrow end portion.Also, a lever 10 used to move the seat 3 up and down is exposed from theoutside of the intermediate supporting body 9.

As shown in FIG. 2, a planar shape of the seat 3 is prolonged in onedirection while rounding as a whole. More particularly, the planar shapeof the seat 3 constitutes a bottle gourd shape consisting of a narrowportion 3 a and incomplete circular portions 3 b extended on both sidesof the narrow portion 3 a. Also, as shown in FIG. 2, the seat 3 isfitted rotatably to a portion, which is deviated from the leg column 1when viewed from the top, of the intermediate supporting body 9.

The back frame 5 is formed into an L-shape that has a horizontal portion5 a at its lower end. The horizontal portion 5 a is fixed to a rearportion of the intermediate supporting body 9 by the welding. Also, arising portion of the back frame 5 is positioned on the outer side of aswiveling area of the seat 3. Therefore, the seat 3 can be swiveledaround and around irrespective of a position of the back frame 5. Inother words, the seat 3 and the back frame 5 can be relatively swiveledarbitrarily. A hollow circle is selected as a cross sectional shape ofthe back frame 5, but other sectional shape such as a hollow square, ahollow ellipse, or the like may be selected.

The back support 4 is an almost plate shape a thickness of which isextremely smaller that an area, and has an almost flat supportingsurface 4′ against which the seated person leans. An outer shape of thesupporting surface 4′ is prolonged in one direction while rounding as awhole. More particularly, like the seat 3, the outer shape of thesupporting surface 4′ constitutes a shape (bottle gourd shape)consisting of a narrow portion 4 a and incomplete circular portions 4 bextended on both sides. The back support 4 is set smaller in size thanthe seat 3, but they may of course be set in almost same size.

The back support 4 is fitted to an upper end portion of the back frame 5via a joint unit 11. Also, the back support 4 can be turned around asecond axis 12 from a fallen position in which the supporting surface 4′is directed forward, as indicated by a solid line in FIG. 1(A), to ahorizontal position in which the supporting surface 4′ is directedupward, as indicated by a dot-dash line in FIG. 1(B) and FIG. 2. Also,the back support 4 can be turned around a first axis 13, which passesthrough a lengthwise and widthwise middle portion in the thicknessdirection, in the fallen position.

A motion of the back support 4 to turn around the first axis 13 is afirst motion, and a motion of the back support 4 to turn around thesecond axis 12 is a second motion. The back support 4 when viewed fromthe front can assume a lengthwise posture or a widthwise postureaccording to the first motion. Also, the back support 4 when viewed fromthe side can change its posture from the fallen position in which thesupporting surface 4′ is directed forward to the horizontal position inwhich the supporting surface 4′ is directed upward according to thesecond motion. The back support 4 adopts a posture that leans slightlybackward in the fallen position.

In this specification, the wording “when viewed from the front” and thewording “when viewed from the side” are employed. In this case, thewording “when viewed from the front” means that the chair is viewed fromthe direction along which the seat 3 is positioned in the near side andthe back support 4 is positioned in the back side (in other words, thedirection along which the user faces to the supporting surface 4′ in asituation that the back support 4 is fallen down), and the wording “whenviewed from the side” means that the chair is viewed from the lateraldirection that intersects orthogonally with the direction of the “whenviewed from the front” and the direction of the “when viewed from thetop”.

Next, details of respective portions will be explained hereunder.

(2) Details of the Seat Receiver Portion

First, details of the seat receiver portion 8 will be explained withreference to FIG. 3 to FIG. 8 hereunder. As understood from FIG. 3 orFIG. 7, for example, a tapered receiving cylinder 14 is secured to theintermediate supporting body 9 and this receiving cylinder 14 is fittedon the upper end portion of the elevating cylinder 1 a. The elevatingcylinder 1 a has a push valve 15 used to switch a free state in whichthis cylinder 1 a can be moved up and down and a lock state in which avertical movement of this cylinder 1 a is inhibited. The push valve 15is projected from an upper surface of the elevating cylinder 1 a. Asalready described, the elevating cylinder 1 a is fitted rotatably intothe outer cylinder 1 b. Therefore, the intermediate supporting body 9and respective members attached thereto can be horizontally swiveledfreely around an axis of the elevating cylinder 1 a.

A lid-like bracket plate 16 is secured to the intermediate supportingbody 9 by the welding. A latter half of the bracket plate 16 constitutesa stepped-down portion 16 a that is set lower than a former half. Alever receiver 18 for holding the lever 10 used to operate the pushvalve 15 of the elevating cylinder 1 a is secured to the stepped-downportion 16 a by the vis 19. The seat 3 is fitted to the portion, whichis distant from the leg column 1, of the bracket plate 16 via a cylinderbody 20 to swivel horizontally. That is, the seat 3 is fitted to theintermediate supporting body 9 in a state that the seat 3 is deviatedfrom the leg column 1 by a certain dimension.

As shown in FIG. 3 and FIG. 7, for example, the seat 3 has a structurethat a cushion 22 is upholstered on a base plate 21 made of the rigidmaterial such as a plywood, or the like. A circular metal (resin) bossmember 23 when viewed from the top is fixed to a center portion of alower surface of the base plate 21. This boss member 23 is fittedturnably into the cylinder body 20 via a bush 24 made of a syntheticresin.

The boss member 23 has a large-diameter portion 23 a that is stacked onthe bracket plate 16. A flange portion 24 a to receive thelarge-diameter portion 23 a of the boss member 23 is formed on an upperend of the bush 24. A plurality of slits 24 b opened downward are formedin the bush 24 discretely along the circumferential direction. The bossmember 23 has a bottom plate 23 b. This boss member 23 can be heldupward-undetachably by screwing the vis 25, which passes through thebottom portion of the intermediate supporting body 9 from the bottom,into the bottom plate 23 b. An upper surface of the intermediatesupporting body 9 is covered with a cover 26 made of a resin.

The lever 10 used for the elevating operation is manufactured by a metalround bar as the material. As shown in FIG. 4 or FIG. 6, for example,the lever 10 is arranged to extend across the intermediate supportingbody 9 when viewed from the top, and both end portions of the lever 10are passed through the intermediate supporting body 9 and exposed toleft and right outer sides of the intermediate supporting body 9. Aresin finger pad 27 is attached to the exposed portions of the lever 10.As shown in FIG. 4 or FIG. 8(A), for example, a portion of the lever 10,which overlaps with the intermediate supporting body 9, is bent like analmost M shape when viewed from the front, and left and right middleportions of the lever 10 constitute a pushing portion 10 a against thepush valve 15 respectively.

Also, a center engaging groove 28 is formed in a middle area of theportion, which is bent like the almost M shape, of the lever 10 to openupward, and a side engaging groove 29 is formed in portions on both leftand right sides respectively to open upward.

Meanwhile, the lever receiver 18 is made of a resin, and has a gutterportion 18 a that is tightly fitted into a portion of the lever 10,which is bent like a downward projected ridge form, from the upper side.A center engaging projection 30 and side engaging projections 31, whichare fitted into the center engaging groove 28 and the side engaginggrooves 29 of the lever 10 respectively, are provided on an upper bottomsurface of the gutter portion 18 a to project downward respectively.

Since the ridge-like bent portion of the lever 10 is fitted into thelever receiver 18, its posture is restricted and thus the lever 10cannot be moved around its axis. Also, as understood from FIG. 8(C),even when the lever 10 is pushed or pulled in any of upward and downwarddirections, such lever 10 is moved around any one of the side engaginggroove 27 and the side engaging projection 31 acting as a fulcrum, andthen the push valve 15 is pushed down.

As shown in FIG. 4, for example, a notch 32 to prevent an interferencewith the lever 10 is formed in the bracket plate 16. Also, holes 33 ofthe intermediate supporting body 9 through which the lever 10 is passedare formed as an elongated hole, which is prolonged in the verticaldirection to allow the vertical rotation of the lever 10, respectively.Also, as shown in FIG. 4, a relief hole 18 b to avoid an interferencewith the elevating cylinder 1 a is opened in the flat plate portion ofthe lever receiver 18.

In the present embodiment, the lever receiver 18 and the lever 10 can bepositioned exactly by fitting the bent portion of the lever 10 into thelever receiver 18. Then, the lever 10 can be fitted simply only when thelever receiver 18 is fixing to the bracket plate 16 by the vis 19 inthis state.

Also, even when the lever 10 is moved in either of the upward anddownward directions, the side engaging groove 29 and the side engagingprojection 31 acting as a turning fulcrum are tightly fitted together.Therefore, there is no disadvantage that the lever 10 is disengaged fromthe lever receiver 18.

In this case, the center engaging groove 28 and the center engagingprojection 30 are not always needed. Also, the engaging projection maybe formed on the lever 10 and the engaging groove may be formed in thelever receiver 18. In addition, the lever receiver 18 may be formed ofmetal. Also, from viewpoints of the convenience in handling and theinsurance of assemble accuracy, it is preferable that the lever receiver18 should be formed as an integral structure like the presentembodiment. But the lever 10 can be held by separate lever receivers attwo locations.

FIGS. 8(D)(E) show another example of the fitting structure of the lever10. In this example, the basic modes of the lever 10 and the leverreceiver 18 are identical to those already described. But this examplehas such a feature that, as a means for preventing the disengagement ofthe lever 10, projections 34 projected outward when viewed from the topare provided to both end portions of the lever 10 exposed from the leverreceiver 18 by the extrusion. Therefore, pairs of the grooves 28, 29 andthe projections 30, 31 provided in the foregoing example are notprovided. As a result, this fitting structure is excellent in strengthand the machining is made simple.

(3) Fitting Structure of the Back Support

Next, a fitting structure of the back support 4 will be explained indetail with reference to FIG. 9 to FIG. 14 hereunder. As shown in FIG.9, for example, the back support 4 has such a structure that a cushion36 is put on a base plate 35 made of the rigid material such as theplywood, or the like. In this case, either the structure in which acloth, or the like is spread on the base plate 35 or the structureconstructed only by the base plate 35 may be employed.

As understood from FIG. 9, for example, the joint unit 11 has a fixedbearing 37 fixed to an upper end of the back frame 5, an auxiliarybearing 38 fitted onto the fixed bearing 37, a rotary bearing (body ofrotation) 40 fitted rotatably to the fixed bearing 37 and the auxiliarybearing 38 by a horizontal supporting shaft 39, a lock pin 41 built inthe rotary bearing 40, a spring (compression coil spring) 42 forenergizing the lock pin 41, and a supporting plate 43 fixed to the backsupport 4.

In the present embodiment, an axis of the supporting shaft 39 serves asthe second axis 12 and an axis of the lock pin 41 serves as the firstaxis 13. The second axis 12 embodied by the supporting shaft 39 extendshorizontally in vicinity of a center portion of the back surface of theback support 4, and its extending direction is set almost parallel witha tangential direction to the seat 3 when viewed from the top.

The fixed bearing 37 has a downward boss portion 37 a, and the bossportion 37 a is fixed to the back frame 5 by the vis 44. Also, an upperportion of the fixed bearing 37 is shaped into a plate portion 37 b thathas a virtual outer shape like a circular plate. A cut-opened portion 45opened toward the opposite side to the seat 3 is formed in the plateportion 37 b. The cut-opened portion 45 is expanded in a range of analmost 90 degree.

The auxiliary bearing 38 has two sheets of circular plate portions 38 athat are stacked on the plate portion 37 b of the fixed bearing 37respectively. Two sheets of circular plate portions 38 a are coupledintegrally via a coupling portion 38 b that is fitted in the cut-openedportion 45 of the fixed bearing 37. Then, as can be seen easily fromFIG. 12, an outer diameter of the coupling portion 38 b of the auxiliarybearing 38 is set smaller than a virtual outer peripheral surface of theplate portion 37 b of the fixed bearing 37. Also, a stepped portion 38 copened upward is formed on an upper end of the coupling portion 38 b ofthe auxiliary bearing 38.

Therefore, an engaging hole 46 opened upwardly is formed by cooperativeactions of the cut-opened portion 45 of the fixed bearing 37 and thecoupling portion 38 b of the auxiliary bearing 38. As shown in FIG. 10,for example, the engaging hole 46 is shaped into a rectangle such that,when viewed from the top, a grove width W1 in the lateral direction(axial direction of the supporting shaft 39) is set larger than a groovewidth W2 in the longitudinal direction. Here, the engaging hole 46 canbe formed directly in the fixed bearing 37. In this case, the auxiliarybearing 38 can be omitted.

The rotary bearing 40 is formed cylindrically as a whole, and its frontend portion is shaped into a forked portion 40 a that is bored to befitted into the plate portion 37 b of the fixed bearing 37 and theauxiliary bearing 38. Also, the forked portion 40 a is fitted to thefixed bearing 37 and the auxiliary bearing 38 by the supporting shaft39. In the present embodiment, a bolt is used as the supporting shaft 39and the supporting shaft 39 is held unreleasably by a nut 47. In thiscase, the nut 47 is held on the rotary bearing 40 not to rotate.

The lock pin 41 is formed to have different diameters such that thefront side has a large diameter, and an engaging projection 48 having analmost rectangular sectional shape is formed on the front end portion.The lock pin 41 is fitted into the rotary bearing 40 to rotate but notto release backwardly. Therefore, a hole 49 formed in the rotary bearing40 is also formed to have stepped different diameters.

Also, the engaging projection 48 of the lock pin 41 has a rectangularsectional shape, while the engaging hole 46 has also a rectangularshape. A dimension L of the engaging projection 48 in the longitudinaldirection (see FIG. 9 and FIG. 10) is set slightly smaller than a groovewidth dimension W1 of the engaging hole 46 in the lengthwise directionbut is set larger than a groove width dimension W2 of the engaging hole46 in the widthwise direction. Therefore, the lock pin 41 when rotatedon its axis has either a posture that is fitted into the engaging hole46 or a posture that is not fitted into the engaging hole 46. The lockpin 41 is pushed toward the fixed bearing 37 by the spring 42 fittedinto its small-diameter portion.

A rear end 41 a of the lock pin 41 is non-circularly notched, and thisrear end 41 a is fitted unrotatably into the supporting plate 43. Then,the base plate 35, the supporting plate 43, and the lock pin 41 of theback support 4 are tightened together by the vis 50 in this state. Thesupporting plate 43 is fixed to the base plate 35 by the vis 51. In thiscase, the lock pin 41 may be fixed to the supporting plate 43. Acylinder portion 43 a for covering the rotary bearing 40 from theoutside is formed on the supporting plate 43.

(4) Motion of the Back Support

As can be seen from FIG. 12 to FIG. 14, a turning angle of the backsupport 4 around the supporting shaft 39 is regulated by a moving strokeof the engaging projection 48 (a moving range on an axis of thesupporting shaft 39) of the lock pin 41. Also, when the back support 4is in its fallen position, the lock pin 41 can be rotated in the rotarybearing 40 and therefore the back support 4 can be turned freely aroundthe axis of the lock pin 41.

When the back support 4 is in its fallen position, a top end of theengaging projection 48 of the lock pin 41 comes in contact with or comesclose to an outer peripheral surface of the coupling portion 38 b of theauxiliary bearing 38. In other words, when the back support 4 is in itsfallen position, the lock pin 41 goes back against the spring 42 in thedirection to come out of the rotary bearing 40. For this reason, it isimpossible basically to move the back support 4 in an axial direction ofthe lock pin 41.

The engaging projection 48 of the lock pin 41 can be fitted into theengaging hole 46 only when it assumes a posture that extends long inparallel with the axial line of the supporting shaft 39 (i.e., awidthwise posture when viewed from the front). In a situation that theengaging projection 48 is not in the posture that extends long inparallel with the supporting shaft 39, as shown in FIG. 13, the engagingprojection 48 of the lock pin 41 stretches over the engaging hole 46when the back support 4 is set upright, so that it is impossible to movethe back support 4 to its horizontal position.

On the contrary, as shown in FIG. 14, when the engaging projection 48 ofthe lock pin 41 assumes the posture that is in parallel with the axialline of the supporting shaft 39 (i.e., the widthwise posture when viewedfrom the front), the engaging projection 48 is fitted in the engaginghole 46, so that the back support 4 can move to its horizontal position.

Then, the engaging projection 48 of the lock pin 41 has a rectangularsectional shape that extends in the same direction as the longitudinaldirection of the back support 4. Therefore, as shown in FIG. 14, it isimpossible to move the back support 4 to its horizontal position unlessthe back support 4 is in a posture that extends long in the tangentialdirection to the seat 3 when viewed from the top. In other words, it isimpossible to move the back support 4 from its fallen position to itshorizontal position until the back support 4 is set in the widthwiseposture.

When the back support 4 assumes the posture that extends long in thetangential direction to the seat 3 when viewed from the top, such backsupport 4 is within an area in which the back support 4 can be supportedstably by the leg 2 (i.e., an area produced by connecting the casters7). Therefore, the chair never falls down even when a large load isapplied to any portion of the back support 4.

In contrast, as shown in FIG. 13(B), when the back support 4 is sethorizontally at a posture that extends long in the radial direction ofthe seat 3 when viewed from the top, an end portion of the back support4 gets out of a stable supporting area of the leg 2. As a result, it ispossible that the chair falls down when the large load is applied to theend portion of the back support 4. However, such situation can beavoided in the present embodiment.

Since the lock pin 41 is fitted into the engaging hole 46 by a pushingaction of the spring 42 in a state that the back support 4 is in itshorizontal position, the back support 4 is held not to fall/turn and notto swivel horizontally. Then, when the back support 4 is lifted from itshorizontal position against the spring 42, the fitting of the lock pin41 into the engaging hole 46 is released, so that the back support 4 canbe turned to the fallen position.

Fitting/unfitting actions of the lock pin 41 into/from the engaging hole46 are classified into a turn regulating function of allowing the backsupport 4 to move to the horizontal position only when such back support4 assumes the widthwise posture when viewed from the front, afall-preventing locking function of holding the back support 4 in itshorizontal position not to fall down, and a horizontal turn preventingfunction of holding the back support 4 in its horizontal position not toturn horizontally. As the means for attaining these three functions, aturn regulating means, a fall-preventing locking means, and a horizontalturn preventing means are needed. In the present embodiment, onestructure is used commonly as three means, but these three means can beprovided by individual structures.

As can be grasped from FIG. 12(A), FIG. 13(A), and FIG. 14(A), thecut-opened portion 45 of the fixed bearing 37 is hidden by the forkedportion 40 a of the rotary bearing 40 irrespective of the posture of theback support 4. Therefore, the cut-opened portion never catches theuser's finger.

In this case, the materials of the bearings 37, 38, 40 are notparticularly limited and, for example, these bearings can be made of aresin, a metal die casting, or the like. The bolt may not be used as thesupporting shaft 39, and the pin may be used and locked by the snapring, or the like. The back support 4 can be fallen down up to thevertical position when viewed from the side. When the back support 4 isused to function as the backrest, it is possible that preferably theback support 4 should be fallen down to lean backward at a slight anglelike the present invention.

(5) Examples of Using Modes of the Chair

The above chair can be used in various modes. First, the seat 3 hasthree using modes, i.e., A. the user sits on the chair in its widthwiseposture, B. the user sits on the chair in its lengthwise posture, and C.the user sits on the chair in its widthwise posture to put left andright shanks on the upper surface of the seat while bending both knees.

Meanwhile, the back support 4 has six using modes, i.e., a. the backsupport is positioned at the back of the seated person in its fallenposition, b. the back support is positioned on the side of the breast ofthe seated person in its fallen position, c. the back support ispositioned on the right side or the left side of the seated person inits fallen position, d. the back support is positioned at the back ofthe seated person in its horizontal position, e. the back support ispositioned in front of the seated person in its horizontal position, andf. the back support is positioned right or left at side of the seatedperson in its horizontal position.

Then, the person can use in various modes based on combinations of usingmodes A to C of the seat 3 and using modes a to f of the back support 4.The back support 4 functions mainly as the backrest in a state that theback support 4 is set to the fallen position.

By the way, sometimes the person wishes to relax by leaning largely thebody while the person is using the chair. In this respect, because boththe seat 3 and the back support 4 have an elongated shape in the presentembodiment, the user can lean largely the upper half of his or her bodyafter the seat 3 is set to the lengthwise posture and the back support 4is set to the longitudinal posture vertically and then the sitting pointis put on the front side of the seat 3. Also, because the back support 4has a long and narrow shape, the seated person can put one arm on theupper surface of the back support 4 while holding the back to the backsupport 4 when the back support 4 is set in the lengthwise posture.

Several examples of the using mode in a state that the back support 4 isset in its horizontal position are shown in FIG. 15. In this case, inFIG. 15, the back support 4 is depicted in the almost same size as theseat 3. In the using example shown in FIG. 15(A), the back support 4 isarranged in parallel with the seat 3 and the person sits on the chair toput the back on the end surface of the back support 4. That is, the backsupport 4 is used as the backrest. Because the narrow portion 4 a existsin the back support 4, the backbone of the seated person never contactsthe back support 4 and therefore the user can use the back support 4without an uncomfortable feeling. Also, as indicated by a dot-dash line,the user can lean the back support 4 in its horizontal position and alsothe user can put both elbows or one elbow behind him or her and put themor it on the back support 4. In other words, the user can use the backsupport 4 as both uses of the backrest and the armrest simultaneously.

In the example shown in FIG. 15(B), the seated person puts the backsupport 4 by his or her side and then uses the back support 4 as thearmrest. When the person uses the back support 4 as the armrest, suchperson can position the back support 4 in front of the seated person andcan put both elbows on the back support 4.

In FIGS. 15(C) to 15(E), an example where the back support 4 is used asa small table is shown. That is, the user can take a note on the backsupport 4 or can put the documents, the notebook computer, or the likeon the back support 4. In FIG. 15(E), the person sits astraddle on theseat 3. Because the seat 3 has the narrow portion 3 a, the seated personcan stretch easily his or her left and right legs and therefore the usercan sits astraddle on the seat 3 in a relaxed posture.

In the example shown in FIG. 15(F), the back support 4 assumes theposture that extends long in front of the seated person (as describedabove, this using mode cannot be employed in the first embodiment). Inthis case, the back support 4 can be used as both the small table andthe armrest. When the back support 4 is set in its horizontal positionwhile the person does not sit on the chair, the user can use both theseat 3 and the back support 4 as a material loading table.

(6) Second Embodiment (FIG. 16)

FIG. 16 shows a second embodiment. This embodiment is a variation of theback support fitting structure in the first embodiment.

In this second embodiment, a reinforcing member 53 is fixed to a top endsurface of the rotary bearing 40 by screws 54. The reinforcing member 53is fitted slidably into a hole 55 formed on the base plate 35 of theback support 4. Also, the reinforcing member 53 is held unreleasably bythe supporting plate 43. In addition, the lock pin 41 is fixed to thebase plate 35 of the back support 4 not to rotate.

In this embodiment, there is such an advantage that, because thereinforcing member 53 is fitted into the hole 55 of the base plate 35,the fitting structure of the back support 4 can be made stouter.

(7) Third Embodiment (FIG. 17)

FIG. 17 shows a third embodiment. This third embodiment is a variationof the first embodiment, and has a feature in the fitting structure ofthe back support 4. A difference of the third embodiment from the firstembodiment is that the engaging projection 48 of the lock pin 41 isformed to have a circular sectional shape.

In this embodiment, the engaging projection 48 has no directionalitywhen such engaging projection is fitted into the engaging hole 46.Therefore, the back support 4 can be moved to its horizontal position nomatter what posture the back support 4 should have in its fallenposition when viewed from the front, and also the back support 4 can beturned horizontally in its horizontal position. Such structure may beemployed in response to the user's desire.

(8) Fourth Embodiment (FIG. 18)

FIG. 18 shows a fourth embodiment. This embodiment has a feature in thejoint unit 11. A basic structure of the joint unit 11 in this embodimentis common to the first embodiment. However, as a different point fromthe first embodiment, an aspect that the lock pin 41 is fitted into therotary bearing 40 not to rotate and an aspect that the back support 4 isfitted to the lock pin 41 to turn can be listed. In this embodiment,there is no constraint in the posture (directionality) when the backsupport 4 is moved to the fallen position and the horizontal position.

(9) Fifth Embodiment (FIG. 19)

FIG. 19 shows a fifth embodiment. This embodiment has a feature in thejoint unit 11. Like the first embodiment, the joint unit 11 in thisembodiment has the fixed bearing 37, the rotary bearing 40, thesupporting shaft 31, the lock pin 41 the spring 42, and the supportingplate 43. However, this joint unit 11 does not have the auxiliarybearing 38 in the first embodiment, and the engaging hole 46 is formeddirectly in the fixed bearing 37. An aspect that the engaging projection48 having a rectangular sectional shape is provided in the lock pin 41is similar to the first embodiment.

Also, the lock pin 41 is held in the base plate 35 of the back support 4not to release and not to rotate relatively, and also is fitted by thevis 50 to slide within a minute distance in the axial direction. A hook57 on which the article such as the bag, or the like is put is fitted tothe fixed bearing 37.

(10) Others

The invention of this application can be embodied into various modesother than the above embodiments. For example, the seat and the backsupport are not limited to the bottle gourd and the circle asillustrated. Various shapes such as almost rectangle, ellipse, rectanglewhose both ends are formed like a circular arc, polygon, circle, and thelike can be set. The seat and the back support can be formed intodifferent shapes. Also, particular structures of the back frame and thejoint unit can be embodied variously as the case may be.

In the case where the back support is a circle or a square and the backsupport can have the first action only, when the back support is fittedsuch that this back support can be turned around the portion that isdeviated from its center portion, a height of the back support can bechanged together with its rotation. Also, the user can play by turningthe back support round and round. Therefore, when the back support canhave the first action only, the back support should not always be shapedinto the elongated shape.

Such a structure can be employed that a height of the back support canbe adjusted independently, or such a structure can be employed that aninterval between the seat and the back support (an interval when viewedfrom the top) can be adjusted. The back support can be folded double.Also, the invention of this application can be applied to the chair ofthe type that the legs are fixed to the floor (i.e., unmovable chair).There is no trouble even if the supporting surface of the back supportis slightly uneven or rounded.

1: A chair comprising: a seat on which a person sits; an almostplate-like back support having a supporting surface against which aseated person is able to lean a back; and a back frame to which the backsupport is fitted via a portion that is different from the supportingsurface; wherein the back support is fitted to the back frame in acondition that at least one motion out of a first motion by which theback support is turned around an axis that extends in a direction topass through the supporting surface and a second motion by which theback support is turned from a fallen position in which the supportingsurface is directed forward to a horizontal position in which thesupporting surface is directed just upward is allowed. 2: The chairaccording to claim 1, where the back support is formed into a long andnarrow shape that has a lengthwise direction and a widthwise directionwhen viewed from a direction facing to the supporting surface, and thefirst motion is given to the back support by fitting the back support tothe back frame such that the back support is turned around a fist axisthat passes through an almost center portion in the lengthwise directionand the widthwise direction. 3: The chair according to claim 1, where arotary bearing that permits the back support to make the second motionis fitted to an upper end portion of the back frame such that the backsupport is turned freely from an almost forward posture to an upwardposture when viewed from a side, and the back support is fitted to therotary bearing to turn around an axis that extends in a direction topass through the supporting surface of the back support and extends in adirection to intersect orthogonally with a rotating axis of a joint. 4:The chair according to claim 1, where the seat is formed into a long andnarrow shape that has the lengthwise direction and the widthwisedirection when viewed from a top, and the seat is supported by legs toswivel horizontally around an almost center portion in the lengthwisedirection and the widthwise direction. 5: The chair according to claim1, where the back frame is supported by a leg column to turnhorizontally, and a swiveling center of the back frame coincides with acenter of the leg column, and the seat is supported by the leg to swivelhorizontally around a position that is deviated from a swiveling centerof the back frame in a horizontal direction. 6: The chair according toclaim 5, further comprising: an intermediate supporting member providedto an upper end of the leg column to swivel horizontally; where the backframe is fixed to the intermediate supporting member and also the seatis fitted to a portion, which is deviated from the leg column to anoutside when viewed from the top, of the intermediate supporting memberto swivel horizontally. 7: A chair according to claim 2, where a planarshape of the seat and an outer shape of the supporting surface of theback support are formed into a bottle gourd shape, a middle portion ofwhich in the lengthwise direction is formed to constitute a narrowportion having a narrowest width and an incomplete circular portion isconnected to both sides of the narrow portion, respectively. 8: Thechair according to claim 3, where a planar shape of the seat and anouter shape of the supporting surface of the back support are formedinto a bottle gourd shape, a middle portion of which in the lengthwisedirection is formed to constitute a narrow portion having a narrowestwidth and an incomplete circular portion is connected to both sides ofthe narrow portion, respectively. 9: The chair according to claim 4,where a planar shape of the seat and an outer shape of the supportingsurface of the back support are formed into a bottle gourd shape, amiddle portion of which in the lengthwise direction is formed toconstitute a narrow portion having a narrowest width and an incompletecircular portion is connected to both sides of the narrow portion,respectively. 10: The chair according to claim 5, where a planar shapeof the seat and an outer shape of the supporting surface of the backsupport are formed into a bottle gourd shape, a middle portion of whichin the lengthwise direction is formed to constitute a narrow portionhaving a narrowest width and an incomplete circular portion is connectedto both sides of the narrow portion, respectively.